Application Pool is auto stopped when browse web application in IIS7 In Sharepoint 2010

I spent a two day attempting to resolve why this was happening in particular WFE server. Every minute I opened my SharePoint site, I’ll get a 503 error and when I check the IIS Console, I discover that the corresponding application pool has stopped. I tried numerous different things, and I also tried the suggestion from this so many MSDN logs .

Resolution:

The first thing that I noticed was that Central Administration and web applications would not come up at all,

Ø    opened IIS and saw the App pools.

Ø  I right-clicked the application pool and started it.  As soon as I tried to browse to Central Administration, and web applications. The same error was repeated.

Ø  Started IIS reset  in both servers(WEF1 , WEF2)
Ø  WEF1  server running fine.
Ø  WEF 2server not started application pools ,,

Ø  After refreshing IIS, I saw that the application pool was stopped again!  Trying this several more times of course yielded the same results.

Ø  Looking through the SharePoint logs indicated a problem with SQL, but everything on the SQL side was functioning properly. Under 14/log files

Ø  However, in looking through the IIS logs, I first came across this error:  “Application pool has been disabled.  Windows Process Activation Service (WAS) encountered a failure when it started a worker process to serve the application pool.” Error event 5059

Ø  opened the Services console (services.msc) and restart the Windows Process Activation Service (WAS), SharePoint related services

Ø  Looking at one of the “Warnings” listed in the IIS log, I saw the following message:  Warning 5029

“The identity of application pool ++++++++ is invalid. The user name or password that is specified for the identity may be incorrect, or the user may not have batch logon rights. If the identity is not corrected, the application pool will be disabled when the application pool receives its first request.  If batch logon rights are causing the problem, the identity in the IIS configuration store must be changed after rights have been granted before Windows Process Activation Service (WAS) can retry the logon. If the identity remains invalid after the first request for the application pool is processed, the application pool will be disabled. The data field contains the error number”.

Ø  Decided to reboot the server , 

Ø  After rebooted the server we try to start application pools in the server but that didn't fix the problem.

Ø  Decided to remove WFE2 server from NLB configuration. 

v  After long research we found some issue  applicationHost.config and machine keys files became corrupted  on the server

v  This IIS Admin configuration 

Ø  Not sure how it happened or what caused it, Might be issue in last server updates

.

Ø  Decided to Changing the Application Pool on a Web Application.

http://blogs.technet.com/b/rycampbe/archive/2011/08/31/changing-the-application-pool-on-a-web-application-the-right-way.aspx

Ø  Created new web application pool  and trying to change the application pool identity to another our domain account with password

Ø  There was an error while performing this operation.

Details: Bad Data. (Exception from HRESULT: 0x80090005)

Ø  Decided to export/import encryption keys for IIS7 from WFE1 server to WFE 2 server.

http://forums.iis.net/t/1172423.aspx

exported iisConfigurationKey from 259 to 260 server but problem was not resolved.

Ø  Updated webapps password in applicationHost.config file  ,

Ø  Reset IIS

Ø  Web application pool’ ‘+++++++’ works again. J

Ø  Understand the exact problem :WAS password key files are corrupted.

     Restore old windows backup files in to the system location.

After restored old applicationHost.config  . Problem was resolved . all web application pools running properly with out any issues.

 Might be useful.